Excavation tools of the types described herein are typically mounted to conventional excavators of the type having a backhoe. The backhoe includes a dipper stick, and the tool is mounted on the outboard end of the dipper stick. The tools are employed for excavation of difficult-to-excavate intermediate substrate, e.g. substrate between the category of loose soil or loose gravel and the category of solid rock. Intermediate substrate requires special tools to be excavated efficiently. Loose soil or gravel can be excavated with a conventional bucket, but a conventional bucket is generally not effective in intermediate substrate. Solid rock excavation generally requires a hydraulic hammer, but a hydraulic hammer is not efficient for excavating intermediate substrate. Attempts have been made to develop tools that are effective and efficient in excavating intermediate substrate. Simply stated, there have been three general approaches, i.e. the single tooth approach; the added articulated tooth approach, in which a tooth is positioned behind the bucket; and the multi-tooth bucket approach, where several teeth are mounted on the back side of the bucket, e.g. as described in Arnold U.S. Pat. No. 4,279,085 and Arnold U.S. Pat. No. 4,457,085. Each of these approaches has been found to have drawbacks and none is efficient and effective for excavation of intermediate substrate.
Other prior art tools include the single pointed ripper (SPR, shown in FIG. 12), which has been around for a long time. It is used for ripping rock and frost, and is very effective because it focuses all of the breakout force on one tooth. Also, while it is relatively smaller and inexpensive, and does the job, it is very slow. (The Multi-Ripper™, Multi-Ripper Bucket™ and DigNRip™ excavation tools, from Leading Edge Attachments, Inc., of Jefferson, Mass., e.g. the latter as shown in FIG. 13, are superior to the SPR because there are three shanks on an arc that focus the breakout force on one tooth at a time, but are more costly.) The SPR usually has an upper structure that is wider than the arm and connects to the linkage of an excavator or backhoe, and a bottom structure formed of a solid slab of steel, making a shank, and a replaceable tooth mounted at the end. The trench made by ripping with the SPR is v-shape because once a predetermined depth is attained, the upper structure interferes with side walls of the trench and the operator is forced to move laterally to clear the sides. After the trench is ripped in the v-shape, the operator changes tools or uses another machine equipped with a bucket to clean the ripped trench of the ripped debris. Since most buckets dig a trench having a flat bottom with bottom corners, the ripped trench has to be at least as wide as the operator's narrowest bucket. Almost all of the forms of SPR available on the market are considerably longer than the standard tip radius of a bucket due to the fact that the ripper is in the center of the top structure, and the top structure hits the sides of the trench. Operators typically look for longer rippers capable of ripping the sides of the trench without having to move laterally. Unfortunately, when the length of a ripper is increased, the breakout force is reduced. The SPR is also favored by operators for prying out boulders, stumps and layers of hard rock formations by wedging the tip under the part to be removed and applying down pressure with the machine. Existing ripper bucket combinations typically do not have a shape that easily allows this function.
The trapezoidal “V” bucket (TVB, shown in FIGS. 14 and 15) is constructed somewhat similarly to the SPR bucket except there are at least two teeth on the bottom horizontal lip and the bucket is considerably wider at the top and bottom. The side leading edges are straight, and the bottom tapers upward quickly. The TVB is generally a light duty bucket used for digging drainage ditches through softer, non-rock materials. There are also versions of the TVB with no teeth (shown in FIGS. 16A and 16B), specifically for digging v-shape trenches through soft dirt. The TVB bucket is not structurally designed for ripping rock or prying.
The cribbing bucket (CB, shown in FIG. 17) is a very narrow bucket construction designed for replacing railroad ties. The long, narrow shape allows the bucket to push the railroad ties from beneath the track. The CB has at least two teeth, and the bucket construction is not in a v-shape. The sides are nearly parallel, and the CB bucket is not structurally designed for ripping or prying.
The strata “V” rock bucket (SVRB, shown in FIG. 18), also known as the Adco “V” bucket, is a v-shape bucket with teeth mounted on the v-shape leading edge, and vertical sides connecting the v-shape leading edges to the upper structure of the bucket. The SVRB is designed for ripping rock; however, the rip radius is long, and as the bucket digs deeper into the rock trench, more and more teeth begin sharing the load, so that the ripping ability is compromised. Many SVRB buckets were sold because operators liked to rip v-shape bottom trenches in the rock for laying utilities, because it saved them from having to rip the rock from the corners of the trench and then backfill material into the corners after the utility line was laid, resulting in savings of time for digging and backfilling. The SVRB bucket eliminates ripping of the bottom corners of the trench; however, the ripping ability is very poor due to a long tip radius and the engagement of multiple teeth at one time. The structure of the SVRB bucket also does not facilitate prying, and it is very expensive because the design requires special cast angle adapters suitable only for the one purpose.